Press control system



Mai-ch 8, 1938. w. ERNST 2 5 PRESS CONTROL SYSTEM Filed Nov. 28, 1934 2 Sheets-Sheet 1 March s, 1938. w. ERNST 2,110,593

PRESS CONTROL SYSTEM Filed Nov. 28, 1934 2 snets-sneet 2 40 J .3 35 L J J I Z. 35 I03 /02 /z7 "1 L -l 29 as 26) H nae/vars Patented Mar. a, 1938 UNITED STATES PATIENT o FIca 2,110,593 mass comer. SYSTEM Walter Ernst, Mount Gilead,

mesne assignments, to

Wilmington, DeL, a corpo- Corporation, Inc., ration of Delaware Ohio, assignor, by The Hydraulic Press Application November 28,1934, Serial No. 755,245 4 Claims. (Cl. 60-52) to reverse the press when a predetermined position of the platen has been reached.

Another object is to provide an electro-me-.

chanical system for the control of presses wherein the pressure exerted by the platen is caused to vary the current supplied to the control circuit,

and this in turn is caused to operate the reversal 20 devices.

Another object is to provide a press control system wherein the press platen is caused to compress a material whose current-carrying ability varies under pressure, such as a pile of 5 carbon plates, this variation of pressure and the consequent variation of current being caused to operate relay devices which in turn actuate the reversal mechanism of the press.

Another object is to provide an arrangement for reversing a press when a predetermined position of the platen has been reached, wherein the pressure exerted by the platen is caused to vary the current-carrying capacity of an electrical circuit, and this in turn is caused to operate a trigger action relay, such as a vacuum tube of the thyratron or grid glow type. the operation of the relay causing the actuation of the press reversal means, such as a reversing valve.

In the drawings:

) Figure l is a diagrammatic front elevation of a press, partly in section, showing the principal mechanical elements in one embodiment of my press control system as applied to a hydraulic press;

Figure 2 is an electrical wiring diagram showing the connections of the various electrical elements in the press control system shown in Figure 1.

Figure 3 is a view of a portion of the circuit of Figure 1, showing a modified construction wherein a solenoid is caused to operate the shift ring of a variable delivery pump.

' Referring to the drawings in detail, Figure 1 shows a press consisting of a base l0, a. top piece II, and strain rods l2 interconnecting the top and base members. The top piece H is provided with a hydraulic cylinder I3 having a piston head I 4 and piston rod IS. The latter is connected to the cally between the guide plates I! attached to the sides of the press. The base III is provided with an anvil-like portion I8 for receiving the work or dies by which the operation of the press is accomplished.

The platen I6 is provided with an extension arm l9 secured thereto and having a portion 20 press platen l6 which re'ciprocates vertl-,

adapted to engage a pile of material, such as the carbon plates 2|, whose current-carrying ability varies under pressure. 'A base 22 supports the carbon pile 2| againstthe thrust ofthe platen arm Ill. The electrical connections of the carbon pile 2| will be described later.

The hydraulic circuit for operating the press consists of a pump 25 of any suitable type, and having a pressure line 26 and a suction line 21. The latter withdraws oil from the tank 28. From the tank 28, a discharge line 29 runs to a reversing valve 30, and conducts fluid from the ports 3| and 3 2-at the opposite ends thereof.

The reversing valve 30 is provided with a valve rod 33 having the spaced heads- 34 and 35. A port 36 serves to admit pressure from the pressure line 26 of the pump, whereas a port 37 is connected to the working or forward line 38 communicating with the space above the piston head it in the hydraulic cylinder i3.

From a port 39, the return line lii runs to the space below the piston head it in the hydraulic cylinder I3. In the return line iii is the high pressure relief valve 4|. From the relief valve ill, the pipe 42 communicates with the discharge line 29 running to the tank 23. The high pressure relief valve 4| is adapted to discharge fluid into the discharge line 29 and tank 28 when the pressure in the line 40 exceeds a predetermined amount. The working or forward line .iil similarly contains a high pressure relief valve t3 having a discharge line 44 communicating with the tank 28 to discharge fluid when the pressure in the line exceeds a. predetermined amount. These relief valves 4i and 43 may be of any suitable type.

The valve rod 33 having the piston heads 34 l and 35 is connected to the armature d5 01 a solenoid 46. The valve rod 33 is urged in the opposite direction to the pull of the solenoid 46 by the coil spring 41 engaging the collar 48, and urging the valve in a righthand direction.

The electrical circuit for the control of the press'is shown in Figure v2. Current is supplied from the power lines 58 and 5| to the primary winding 52 of a transformer 58. The transformer 58 is provided with suitable secondary windings 54, 55, and 58. From the secondary winding 55, the line 51 runs to one terminal of the current-varying unit or carbon pile 2|. From the opposite terminal of the carbon pile 2 l the line 58 runs tov the grid 59 of the vacuum tube 88 by way of the resistor 8|. Between the line 82 running from the opposite terminal of the transformer secondary 55 and the line 58 is arranged the capacitor 88. The line .82 continues to the negative pole of the battery or other current source 54, the opposite or positive terminal of which is connected by the lines and 88 to the electrode 81 of the vacuum tube 88. The electrode 81 is heated by the filament 88, current being supplied for this purpose by the lines 89 and 18 running from the transformer secondary The lines 85 and 88 are connected by the line 1| to the negative terminal of the battery or other source of current 12. From the positive terminal of the latter, the line 18 runs to one terminal of the operating coil 14 of the normally-closed electro-magnetic switch 15, having the armature 15. The opposite terminal of the operating coil 14 is connected by the line 11 to the plate 18 of the vacuum tube 88. A spring 19 urges the switch bar 15 into a normally-closed position.

One terminal of the transformer secondary 54 is connected by the line 88 to the manual switch 8| and thence by the line 82 to the upper switch bar 88 of the normally-open contactor switch 84. The line 85 runs to the lower switch bar 85 thereof. The switch bars 88 and 88 of the contactor switch 84 are urged into normally-open positions by the spring 81.

The fixed terminal of the electro-magnetic switch bar 15 and of the upper contactor switch bar 88 are interconnected by the line 88. From the fixed terminal of the lower contactor switch bar 86, the line 89 runs to one terminal of the solenoid 48, from the opposite terminal of which the line 98 runs to the transformer secondary winding 54. From the latter the line 9| runs to the operating coil 92 of the contactor switch 84, and from the opposite side thereof, the line 98 runs to one terminal of the manual switch 8|; whencethe line 94 runs to the electro-magnetic switch bar 15. The contactor switch 84 is pro vided with an armature 95, engaging the switch bars 88 and 85, and actuated by the operating coil 92 in the manner described below.

In operation, the press is started by closing the manual switch 8|, which is preferably of the push button variety. Current from the transformer secondary 54 is then caused to energize the'operating coil 92 of the contactor switch 84 by way of the line 88, switch 8|, and lines 98 and 9|. The consequent closing of the switch bar 88 against the urge of the spring 81 causes the operating coil 92 to be henceforth energized when the switch 8| is released. The holding circuit thereof includes the lines 88 and 82, the switch bar 88, the line 88, the normally-closed switch bar 15, and the lines 94, 98 and 9| to the transformer'secondary 54. The closing of the lower switch bar 88 causes the winding of the solenoid 48 to be likewise energized from the transformer secondary 85, the switch bar 88, and the lines 88 and 88.

The sue on of the solenoid 48 causes its armature 45and the valve rod 88 to be shifted to the left, causing thevalve heads 84 and 88 tobe 54 through the lines 88, 82, and 1 moved into the dotted positions shown in Figure 1, against the urge of the coil spring 41. Pressure fluid now passes from the pump 25 and the pressure line 28 through the middle chamber of the valve 88, out the port 81 and through the working line 88 to the chamber above the piston head l4, causing the latter to move down, to-

platen l8. The fluid discharged from the chamber beneath the piston head l4 passes through the return line 48, and the port 89 into the rlghthand end chamber of the valve 88, thence through the port 82 into the discharge line 29 running to the tank 28. The relief valves 4| and 48 serve to constantly pass the fluid therethrough and do not influence the operation of the circuit except when an excessive pressure deveiops.

As the platen moves downward and engages the work, its arm l9 compresses the carbon pile 2|, causing its electrical resistance to be decreased. As this occurs, current is permitted to flow therethrough in increasing amounts from the transformer secondary 55, by way of the lines 51 and 58, changing the potential of the grid 59 in the vacuum tube 88.

The vacuum tube 88 is preferably of the socalled thyratron or grid glow'type, wherein a substantially constant voltage drop exists between the cathode 61 and the anode or plate 18. The potential of the grid 59 is kept negative by the battery 64. When the potential of the grid 59, however, exceeds a predetermined amount, the vacuum tube 88 suddenly becomes operative, causing the electron flow to conduct current through the'circuit represented by the lines 18 and 11, the operating coil 14 of the contactor switch 15, the battery 12, the lines 1| and 88, the cathode 81 and plate 18.

The vacuum tube 88 thus acts, in efiect, like a relay which is operative only when the current supplied to the grid thereof exceeds the firing potential of the tube. The trigger action of the tube 58 is not operative until the current passed by the carbon pile 2| attains a suflicient magnitude through the lowering of the resist ance thereof by the compression of the carbo pile.

The energization, in this manner, of the operating coil 14 of the electromagnetic switch 15 lifts the armature 18 and the switch bar thereof, opening the circuit between the lines 94 and 88 against the urge of the spring 19. This breaks the holding circuitof the contactor switch coil 92, causing the latter to become de-energized and the switch bars 88 and 88 thereof to be opened by the urge of the spring 81. The opening of the switch bar 88 breaks the 'circuit between the lines 85 and 89, and consequently de-energizes the windings of the solenoid 48, permitting the valve rod 88 to be urged to its righthand position under the influence of the coil spring 41.

Under the urge of the spring 41, the valve heads 84 and 85 take the righthand positions, as shown by the solid lines in Figure 1. Under these circumstances, pressure fluid flows from the pressure line 28 of the pump 25 through the middle chamber of the valve 88 and the line 48 and the relief valve 4| into the space beneath the piston head |4, causing the latter to rise and the platen l8 to be retracted. The fluid in the space above the piston head |4 retu'rnsto the tank 28 by way of the line 88, the relief valve 48, the port 81, the lefthand end chamber of the valve 88, the port 8| andthedischargeline2t b pl mesupwarduntilitm the relief valve 4| will then cause the pressure fluid to be discharged through the line 42 intothe tank 28 by way of the discharge line 29.

As the platen i6 nears the top of its stroke,

it may be caused to operate a positionally responsive switch 98, breakingthe circuit in the.

line 11, and consequently de-energizing the plate circuit of the vacuum tube 80. Some arrangement of this sort is advisable, since the "thyratron or grid glow tubes have the peculiarity of starting operation when the grid potential exceeds the firing potential but of not stopping when the grid potential subsequently falls below the "firing potential. The opening oi the switch 98 by the platen l6 at the top of its stroke de-energizes the coil 14 of the electromagnetic switch 15 and allows its switch bar to bereturned to its normally-closed position under the influence of the coil spring 19.

To re-start the press i'or another working stroke, the switch button 8i is again depressed, and the foregoing cycle 01' operations repeats itsell. As the platen passes downward, however, it releases the positionally-responsive switch 98, thus again closing the circuit in the line l1 and placing the plate circuit again in condition for operation. It will be understood, however, that if alternating current is utilized in place of the direct current from the direct current source 12 to energize the plate circuit, the operation of the tube may be interrupted by the phase change thereof.

It will be understood that instead of the reversing valve 30 and ,the constant delivery pump 25, a variable delivery pump having its fluid lines i 26 and I2! connected respectively to the forward and return lines 38 and 40 may be used and the flow thereof varied. by suitable electrical means responsive to the action of the electrical circuit described above. For example, in Figure 3, the armature 45 of the solenoid 48 is operatively connected to the flow-varying or shitting ring ll of a variable delivery pump I00, and the'subsequent shifting thereof brought about by the operation of the solenoid 46 is thus caused to reverse the flow of the fluid in the pipe lines 38 and 40 without the necessity for employing the reversing valve 30. For the p oi compensating for the unequal supply of fluid required on opposite sides oi the piston head ll, due to the space occupied by the piston rod ID, a compensating valve I0! is arrangedbetween the pipes 30 and 40 with its end chambers connected thereto. Its middle chamber is connected to the line 21' from the fluid tank 28, and its valve element I03 automatically moves to and fro to permit fluid to be drawn from the tank 28 into the space below the piston head H, or' to be discharged from the space above it. The details of the compensating valve I02 i'orm no part 01' the present invention, and will be found i'ully disclosed in the United States Patent No. 1,653,350, granted on December 20, 1927 to Walter Ernst.

It will be understood that r desire to comprehend within my invention such modifications as may benecessary to adapt it to varying conditions and uses.

- Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In combination, a hydraulic press having a reversibly movable plunger, a pump, fluid-reversing means for reversibly distributing the pressure fluid from said pump to said plunger, an electrically-controlled shifting element for shifting said ation of said plunger, and an electrical device operatively responsive to the reception of a predetermined current from said current-varying instrumentality to change the electrical condition 01! said electrically-controlled shitting element and thereby bring about the shifting of said fluid-reversing means.

2. In combination, a hydraulic press having a reversibly movable plunger, a pump, fluid-reversing means for reversibly distributing the pressure fluid from said pump to said plunger, an electrically-controlled shifting element for shifting said fluid-reversing means, a current-varying instrumentality responsive to the application of pressure for varying the electric current passing therethrough, means associated with said plunger for simultaneously transmitting pressure to a work-piece and said instrumentality upon operation 01' said plunger, and a vacuum tube relay operatively responsive to the reception of a predetermined current irom said current-varying instrumentality to change the electrical condition of said electrically-controlled shifting element and thereby bring about the shifting oi. said fluidreversing means.

3. In combination, a hydraulic press having a reversibly movable plunger, a pump,- fluid-reversing means for reversibly distributing the pressure fluid from said pump to said plunger, an electrically-controlled shifting element for shii'ting said fluid-reversing means, a current-varying instrumentality responsive to the application of pressure for varying the electric current passing therethrough, means associated with said plunger for simultaneously transmitting pressure to a work-piece and said instrumentality upon operation-of said plunger, and an electrical device operatively responsive to the reception of a predetermined current from said current-varying instrumentality to change the electrical condition 01' said electrically-controlled shifting element and thereby bring about the shifting of said fluidreversing means, said current-varying instrumentality comprising a pile of carbon elements.

4. In combination, ahydraulic press having a reversibly movable plunger, 9. pump, fluid-reversing means for reversibly distributing the pressure fluid from said pump to said plunger, an electrically-controlled shitting element for shifting said fluid-reversing means, a current-varying mm d Valve.

. WALTER 

